Circuit breaker electronic trip unit without special transformer for ground current sampling

Abstract

The invention relates to a circuit breaker electronic release free of a grounding current sampling special instrument transformer. The electronic release is characterized in that main loop current is used for converting phase current into low-voltage potential signals through three-phase air-core circuit instrument transformers respectively; the three-phase air-core circuit instrument transformers are connected to a phase line current sampling processing circuit of an original electronic type circuit breaker electronic release, and are connected to three groups of low-pass active filter circuits consisting of resistors, capacitors and integrated circuits for filtering electromagnetic interference in the main loop; filtered each-phase potential signals enter a subtraction circuit formed by a resistor and an integrated circuit so as to carry out operation on the signals; and the operation result is subjected to inverting amplification through a proportioning operational amplifier consisting a resistor and an integrated circuit, and grounding current signals which are collected and subjected to operation access to an analog-digital (AD) conversion port of a microprocessor for being processed. According to the electronic release disclosed by the invention, when the grounding current signals are sampled, the grounding current sampling special instrument transformer is omitted, the manufacturing cost is reduced, the installation volume is reduced, the accessing difficulty of the circuit breaker in an operation system is improved, and the structure is simple.

Description

technical field [0001] The invention belongs to an electronic release device for a low-voltage circuit breaker, in particular to an electronic release device for a circuit breaker without a special transformer for ground current sampling. Background technique [0002] At present, the grounding protection of low-voltage electrical appliances, especially electronic circuit breakers, generally adopts the principle of zero-sequence current sampling to collect signals. The rear side of the circuit breaker should be spliced ​​with a zero-sequence current transformer with three-phase metal conductors injected and sealed with insulating materials, which will increase the overall installation volume of the circuit breaker, increase the overall cost of the circuit breaker, and increase the volume of the complete set of cabinets , or affect the overall installation behavior. Contents of the invention [0003] In order to solve the technical problems in the known technology, the pres...

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Problems solved by technology

[0002] At present, the grounding protection of low-voltage electrical appliances, especially electronic circuit breakers, generally adopts the principle of zero-sequence current sampling to collect signals. The rear side of the circuit breaker should be spliced ​​with a zero-sequence current transformer with three-phase metal conductors injected and sealed with insulating materials, which will increase the overall installation volume of the circuit breaker, increase the overall cost of the circuit breaker, and increase the volume of the complete set of cabinets , or affect the overall installation

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